Hues are designated by color names: Red (R), Green (G), Yellow (Y), Blue (B), etc. According to a model by Albert Henry Munsell (1858 to 1918), a distinction is made between five main color tones, in addition to the ones mentioned, purple (M) and another five intermediate color tones, namely yellow- red, green-yellow, blue-green, purple-blue and red-purple. These ten hues, arranged evenly in a circle diagram, make up the color wheel, where the zero point is at red. In the color circle, the hue is defined by the angle. Red has the angle 0°, yellow 60°, green 120°, cyan 180°, blue 240° and magenta 300°.
Hues, together with color saturation, form the chromaticity. The human eye can distinguish approx. 130 different color tones.